The police's failure to conduct an overarching examination of state collusion with a notorious loyalist murder gang in Northern Ireland was inconsistent with its human rights obligations, a judge has found.

The independent Historic Enquiries Team (HET) had partially completed a probe into the activities of the Glenanne gang before its work was halted by Police Service of Northern Ireland (PSNI) commanders.

The HET had examined individual murders committed by the gang but had not undertaken an overarching thematic review of the collusion allegations.

The PSNI's decision to stop the HET review was challenged by way of judicial review by the family of one of the gang's victims.

The Glenanne gang was a unit of the Ulster Volunteer Force (UVF) that counted rogue security force personnel among its members.

Operating mostly in Tyrone and Armagh, the gang has been blamed for around 130 sectarian murders during the 1970s and 1980s.

The judicial review was taken by the family of Patrick Barnard, who was killed in a bomb blast in Dungannon in 1976.

Delivering judgment at Belfast High Court, Judge Seamus Treacy found that changes made by the PSNI to how it investigated historic cases were "fundamentally inconsistent" with its obligations in the European Convention on Human Rights.

He also questioned the state's commitment to investigating cases that involved alleged collusion.

He was particularly critical of decisions taken by former PSNI chief constable Sir Matt Baggott.

The judge said the Barnard family had a "legitimate expectation" that a thematic probe into collusion would have been completed.

He said the police's treatment of them had been "unfair" in the "extreme".

"It has completely undermined the confidence of the families whose concerns are not only still unresolved but compounded by the effects of the decisions taken by the then chief constable (Mr Baggott)," he said.

Justice Treacy added: "There is a real risk that this will fuel in the minds of the families the fear that the state has resiled from its public commitments because it is not genuinely committed to addressing the unresolved concerns that the families have of state involvement."

The judge placed the onus on the PSNI to offer an "appropriate form of relief" that would address the family's concerns.

The court was packed with relatives who lost loved ones at the hands of the murderous gang.

Outside, some wept and others applauded as they reflected on the judgment.

Patrick Barnard's brother, Edward, who took the judicial review, said he had not expected the outcome.

"I am shocked. I did not think we would get the victory today that we have got," he said.

"We have proved collusion, we have proved that the police halted the report, they stopped the HET from fulfilling their part."

Eugene Reavey, whose three brothers were murdered by the gang in 1976, described the alleged collusion as a "war crime".

"The judge repeated collusion, collusion, collusion all day," he said.

"This was a war crime - there were 135 people dead. This was murder by the state and its agents.

"There is no other word for it than a war crime - that's how big it is.

"I am delighted for everybody here for the perseverance they have shown over the years. We have been humiliated, we have been abused by everybody in every part of the journey but today we have been vindicated."

Darragh Mackin, solicitor for Mr Barnard, said the families had been through an "excruciating" process.

"This has been a long and turbulent journey for these families," he said.

"Not only has the court today ruled that there is credible evidence (of collusion) throughout the Glenanne series but the procedure and torment that these families have had to go through has been extremely unfair and there has been an abuse of power by the powers-that-be."